1. Field of the Invention
The present invention relates to a detector responsive to interactions of variable intensity. The invention also relates to a method of detecting the intensity of interactions.
2. Description of the Related Art
A detector responsive to mechanical interactions of variable intensity is shown in U.S. Pat. No. 6,501,465, in which conducting fabric planes are brought into electrical contact through a separator layer when pressure is applied. Voltages are applied to the conductive layers in order to identify the position of the interaction and a measurement of current provides an indication of the intensity of the interaction due to an applied force, an area of interaction or an applied pressure.
It is known that detectors of this type are reliable in terms of identifying an XY location in a two-dimensional plane but difficulties are encountered in terms of their sensitivity to applied pressure in the Z direction. An enhancement is disclosed in U.S. Pat. No. 6,452,479 where it is possible to control the level of sensitivity and reduce instances of false triggering.
A quantum tunnelling composite is disclosed in U.S. Pat. No. 6,291,568 which exhibits electrically insulating properties until pressure is applied thereto, whereupon the composite becomes conductive. The relationship between the intensity of the applied mechanical interaction and the extent to which the composite becomes conductive may be controlled and experience has shown that this approach provides better accuracy and sensitivity for detecting intensities of applied interactions in the Z direction, compared to conductive planes that are primarily configured for identifying XY position.
The present inventors have experimented with deploying a quantum tunnelling composite for detectors of the aforesaid type and the non-linear properties of the material have been documented. Thus, it is known that a detector may be designed that exhibits high sensitivity to low intensities or alternatively the sensitivity may be reduced such that the range of operation is increased. However, difficulties persist in terms of designing a detector that is sensitive to low intensities, often referred to as a first touch, while at the same time being responsive to a wide range of applied intensities.